Abstract/Summary

The modest aim of this paper is to present records and observations of bat activity in Ogof Draenen. The records are predominantly collated from those made by cavers since the discovery of the cave system in 1994. Most of these records are unsystematic in nature, and are likely to be biased towards the more visible Horseshoe bats (which make up the vast majority of sightings), perhaps under-representing the more cryptic Myotis species. Nonetheless they help to provide a coherent picture of the way that bats use what is now probably Britain’s longest cave. Bat activity is temporally concentrated to the winter months, and suggests that Lesser Horseshoes in particular exploit the deeper cave passages as solitary hibernation roosts in winter, probably moving dynamically in response to cold weather. There is little evidence of summer usage. Spatially, activity is concentrated in the relict passages close to the known hibernaculum at Siambre Ddu, with only occasional sightings elsewhere in the cave. The density of sightings is shown graphically and compared with the recorded distributions of guano accumulations and bat skeletons, and suggests a similar spatial usage now and historically, even though animal densities were formerly much higher and might once have involved summer usage of the cave. Dustings of faecal pellets throughout the cave suggest that bats may also use the entire system in a much more diffuse manner. Ogof Draenen therefore provides an important site for hibernation activity for several bat species, predominantly centred on the hibernaculum at Siambre Ddu.